Table 1. Crystal and experimental data for (NH₄)₂NbOF₅ .

	297 K	233 K	198 K
Crystal data
Chemical formula	F5NbO·2H4N	F5NbO·2H4N	F5NbO·2H4N
Mr	239.99	239.99	239.99
Cell setting, space group	Orthorhombic, Cmc21	Monoclinic, C2	Monoclinic, Ia
Temperature (K)	297 (2)	233 (2)	198 (2)
a, b, c (Å)	5.9915 (3), 14.4518 (8), 7.1999 (4)	14.4051 (9), 5.9715 (3), 7.2312 (3)	14.3384 (14), 5.9804 (6), 14.4524 (14)
β (°)	90.00	90.195 (3)	90.110 (3)
V (Å3)	623.42 (6)	622.02 (6)	1239.3 (2)
Z	4	4	8
Dx (Mg m−3)	2.557	2.563	2.573
Radiation type	Mo Kα	Mo Kα	Mo Kα
μ (mm−1)	1.97	1.97	1.98
Crystal form, color	Sphere, colorless	Sphere, colorless	Sphere, colorless
Crystal size (mm)	0.32 × 0.32 × 0.32	0.32 × 0.32 × 0.32	0.32 × 0.32 × 0.32
Data collection
Diffractometer	Bruker SMART 1000 CCD	Bruker SMART 1000 CCD	Bruker SMART 1000 CCD
Data collection method	ω scans	ω scans	ϕ and ω scans
Absorption correction	Multi-scan	Multi-scan	Multi-scan
Tmin	0.572	0.571	0.570
Tmax	0.572	0.571	0.570
No. of measured, independent and observed reflections	8132, 1881, 1806	8132, 3062, 3003	16 431, 6354, 5715
Criterion for observed reflections	I > 2σ(I)	I > 2σ(I)	I > 2σ(I)
Rint	0.028	0.025	0.025
θmax (°)	39.0	39.0	39.0
Refinement
Refinement on	F2	F2	F2
R[F2 > 2σ(F2)], wR(F2), S	0.017, 0.049, 1.08	0.019, 0.052, 1.14	0.023, 0.057, 1.05
No. of reflections	1881	3062	6354
No. of parameters	61	84	165
H-atom treatment	Not refined	Not refined	Not refined
Weighting scheme	w = 1/[σ2(F) + (0.0301P)2 + 0.0923P], where P = (F + 2F)/3	w = 1/[σ2(F) + (0.0261P)2 + 0.3566P], where P = (F + 2F)/3	w = 1/[σ2(F) + (0.0199P)2 + 1.2051P], where P = (F + 2F)/3
(Δ/σ)max	0.040	0.020	0.108
Δρmax, Δρmin (e Å−3)	0.57, −0.41	0.99, −0.97	0.89, −1.28
Extinction method	SHELXL97	SHELXL97	SHELXL97
Extinction coefficient	0.1814 (17)	0.1807 (13)	0.02053 (17)
Absolute structure	Flack (1983 ▶)	Flack (1983 ▶)	Flack (1983 ▶)
Flack parameter	0.0 (2)	0.0 (3)	0.11 (10)

Computer programs used: SMART (Bruker, 1998 ▶), SAINT (Bruker, 2000 ▶), SHELXTL (Sheldrick, 2008 ▶).